Rheology of faults in subduction zones and its implications for the generation of slow earthquakes

2015 Fiscal Year Final Research Report

• Project/Area Number: 25287135
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: Hirose Takehiro 国立研究開発法人海洋研究開発機構, 高知コア研究所, グループリーダー代理 (40470124)
• Co-Investigator(Renkei-kenkyūsha): Tanikawa Wataru 国立研究開発法人海洋研究開発機構, 高知コア研究所, 主任研究員 (70435840) ; Takahashi Miki 国立研究開発法人産業技術総合研究所, 活断層・地震研究センター, 主任研究員 (40470033)
• Research Collaborator: Sawai Michiyo ; Noda Yoji
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: スロー地震 / 断層 / 摩擦

Outline of Final Research Achievements

Slow earthquakes in subduction zones have been considered as the key phenomenon associated with megathrust earthquakes. Several mechanisms have been proposed, but the cause of slow earthquakes remains elusive. One possibility is that an increase in pressure of pore fluid promote slow slip in subduction faults, yet role of fluid pressure in mechanics of slow earthquakes is poorly understood. Therefore, we conducted friction experiments on blueschist fault rocks to investigate the influence of effective stress on frictional behavior. Our results show a transition from stable to unstable behavior with decreasing effective normal stress, which is mechanically equivalent to increasing fluid pressure. This transition is a prerequisite for generating slow earthquakes. Our results imply that high pore pressures are a key factor for nucleating slip leading to slow earthquakes.

Free Research Field

岩石力学・構造地質